Particle Beam System

ABSTRACT

A particle beam system comprises a particle beam source  5  for generating a primary particle beam  13 , an objective lens  19  for focusing the primary particle beam  13  in an object plane  23 ; a particle detector  17 ; and an X-ray detector  47  arranged between the objective lens and the object plane. The X-ray detector comprises plural semiconductor detectors, each having a detection surface  51  oriented towards the object plane. A membrane is disposed between the object plane and the detection surface of the semiconductor detector, wherein different semiconductor detectors have different membranes located in front, the different membranes differing with respect to a secondary electron transmittance.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority of German Patent Application.No. 10 2009 008 063.5, filed Feb. 9, 2009, entitled “PARTICLE OPTICALSYSTEM”, the contents of which are hereby incorporated by reference intheir entirety.

FIELD OF THE INVENTION

The invention relates to a particle beam system having a particle beamsource for generating a primary particle beam and an electron detectorand an X-ray detector.

BACKGROUND OF THE INVENTION

A conventional particle microscope comprises a particle beam source forgenerating a primary particle beam and an electron detector. Theparticle microscope can be an electron microscope having an electronbeam source as its particle source, and the particle microscope can bean ion microscope having an ion source as its particle source. Someconventional electron microscopes include an X-ray detector fordetecting X-rays generated by the primary electron beam at an inspectedobject. An energy spectrum of such X-rays may comprise characteristiclines indicative of elements included in the object. An analysis of theX-rays may comprise an analysis with respect to energy of detectedX-rays. One example of such analysis is an analysis commonly referred toas Energy Dispersive X-ray Spectroscopy (EDX). A conventional electronmicroscope including an X-ray detector is known from US 2006/0138325 A1.The X-ray detector of this microscope receives X-rays originating froman object and generated at the object by a primary electron beam focusedonto the object. Since the primary electron beam also generatessecondary electrons, which should not be detected by the X-ray detector,the X-ray detector comprises an electron trap to prevent secondaryelectrons from generating detection signals in the X-ray detectors. Suchdetection signals generated by secondary electrons could be erroneouslyinterpreted as X-ray signals in a subsequent analysis. The electron trapmay comprise a magnetic electron trap.

A detection efficiency for X-rays has been perceived as being too low inconventional electron microscopes including an X-ray detector. Thisperceived lack of efficiency applies in particular in a situation wherethe primary electron beam has a low energy.

SUMMARY OF THE INVENTION

The invention has been accomplished taking the above problems intoconsideration.

Embodiments of the invention provide a particle beam system comprising aparticle beam source, an electron detector and an X-ray detector havinga relatively simple configuration. Other embodiments of the inventionprovide a particle beam system comprising a particle beam source, anelectron detector and an X-ray detector having an improved performancewith respect to X-ray detection.

According to embodiments, a particle beam system comprises a particlebeam source configured to generate a primary particle beam, an objectivelens configured to focus the primary particle beam in an object plane,an X-ray detector having at least two semiconductor detectors, whereineach of the semiconductor detectors has a detection surface orientedtowards an object disposed in the object plane for inspection, andwherein a membrane or window is located between the object and thedetection surface of the respective detector. The membranes located infront of the at least two semiconductor detectors differ with respect toa transmittance for secondary electrons.

The X-ray detector does not comprise any magnetic electron traps. Theinventors found that magnetic electron traps of an X-ray detectorlocated close to an objective lens of an electron microscope may disturbelectromagnetic fields generated by the objective lens for focusing theprimary electron beam. Such disturbance of the electromagnetic fieldsgenerated by the objective lens may affect the focusing of the primaryelectron beam, which may finally reduce a performance of the system.

In the X-ray detector according to the embodiment, secondary electronsmay penetrate the membrane provided in front of the semiconductordetector such that they generate detection signals in the semiconductordetector and are detected accordingly. However, since two differentmembranes are provided which differ with respect to their transmittancefor secondary electrons, different amounts of secondary electrons willpenetrate the membranes such that different amounts of detection signalswill be generated which originate from detection events triggered byelectrons. It is thus possible to determine an amount of detectionevents caused by electrons for at least one of the semiconductordetectors. A remaining amount of detection events not caused byelectrons will then represent an amount of detected X-ray events. It isthus possible to obtain a relatively accurate detection of X-ray amountswithout having to use a magnetic electron trap, for example.

According to a further embodiment, the X-ray detector comprises a ringstructure surrounding a beam path of the primary particle beam, whereinthe ring structure carries at least two semiconductor detectors suchthat detection surfaces of the semiconductor detectors are orientedtowards an object plane of the objective lens. According to exemplaryembodiments herein, the IP-ray detector comprises more than twosemiconductor detectors, such as, for example, three, four, eight ormore semiconductor detectors. According to some embodiments, thedetection surfaces of the plural semiconductor detectors may be arrangedin a common plane. According to other embodiments, the semiconductordetectors and the detection surfaces thereof may be shaped as sectors,such that the plural detection surfaces together substantially fill acircular surface having a central aperture allowing the primary particlebeam to traverse the X-ray detector.

According to further embodiments, a particle beam system comprises aparticle source for generating a primary particle beam, an objectivelens for focusing the primary particle beam in an objective plane, anelectron detector for detecting electrons originating from an inspectedobject, and an X-ray detector including a first semiconductor detectorhaving a detection surface oriented towards the object plane. Theparticle beam system may further comprise an actuator and a firstmembrane, wherein the actuator is configured to move the first membraneback and forth between a first position and a second position, whereinthe membrane is disposed between the semiconductor detector and theobject plane when it is located in the first position, and wherein thefirst membrane is not located between the semiconductor detector and theobject plane. When the first membrane is not located between thesemiconductor detector and the object plane, X-rays generated by theprimary particle beam at the object can be incident on the detectionsurface of the semiconductor detector without having to traverse themembrane. On the other hand, when the first membrane is located betweenthe semiconductor detector and the object plane, X-rays generated by theprimary particle beam at the object have to traverse the membrane toreach the detection surface of the semiconductor.

The first membrane which can be selectively disposed between the firstsemiconductor detector and the object plane has a transmittance forelectrons which is smaller than 1. It is both possible to vary adetection sensitivity for secondary electrons of the semiconductordetector by placing the first membrane in front of the semiconductordetector and by removing the membrane from its position in front of thesemiconductor detector. Similar to the embodiment having two differentmembranes located in front of two different semiconductor detectors, itis thus possible to perform two subsequent measurements of detectionevents, wherein the two measurements differ with respect to thetransmittance for electrons. From these two measurements it is possibleto determine an amount of detection events caused by X-rays with arelatively high accuracy.

According to an exemplary embodiment herein, a second membrane isprovided which is also coupled to the actuator, wherein the secondmembrane is positioned in front of the semiconductor detector when thefirst membrane is not positioned in front of the semiconductor detector,and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

The forgoing as well as other advantageous features of the inventionwill be more apparent from the following detailed description ofexemplary embodiments of the invention with reference to theaccompanying drawings. It is noted that not all possible embodiments ofthe present invention necessarily exhibit each and every, or any, of theadvantages identified herein.

FIG. 1 is a schematic illustration of a particle beam system;

FIG. 2 is a sectional view along a line II-II in FIG. 3 of an X-raydetector of the particle beam system shown in FIG. 1;

FIG. 3 is an elevational view of a bottom of the X-ray detector shown inFIG. 2;

FIG. 4 is a graph illustrating a transmittance for electrons ofmembranes of the X-ray detector shown in FIGS. 2 and 3;

FIG. 5 shows a graph illustrating a transmittance for X-ray radiation ofthe membranes of the X-ray detector shown in FIGS. 2 and 3;

FIG. 6 shows a graph illustrating or rates detected by the X-raydetector shown in FIGS. 2 and 3;

FIG. 7 is a schematic illustration of a portion of a particle beamsystem; and

FIG. 8 is an elevational view from the bottom of a particle beam system.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the exemplary embodiments described below, components that are alikein function and structure are designated as far as possible by alikereference numerals. Therefore, to understand the features of theindividual components of a specific embodiment, the descriptions ofother embodiments and of the summary of the invention should be referredto.

FIG. 1 is a schematic illustration of an exemplary embodiment of aparticle beam system 1. The particle beam system 1 comprises an electronbeam source 5 having a cathode 7 and extractor and suppressor electrodes9 for generating a primary particle beam 13. The primary particle beam13 traverses a condenser lens 11, an aperture 15 provided in an electrondetector 17, and an objective, lens 19 for focusing the primary particlebeam 13 at a location 21 in an object plane 23. A surface of an object25 to be inspected is disposed in the object plane 25.

The objective lens 19 comprises a ring coil 27 provided in a ring-shapedyoke having a ring-shaped upper pole piece 31 and a ring-shaped lowerpole piece 32 such that a ring-shaped gap is formed between the upperand lower pole pieces 31, 32. A magnetic field for generating theelectron beam 13 is generated in this gap.

The particle beam system 1 further includes a beam tube 35 which entersand partially traverses the objective lens 19. An end electrode 37 isprovided at a bottom end of the beam tube 35. A terminal electrode 36 isdisposed between the end electrode 37 and the object plane, wherein anelectrostatic field generated between the end electrode 37 and terminalelectrode 36 provides a focusing power on the primary electron beam 13.The focusing power provided by the electrostatic field between theelectrodes 36 and 37 and the focusing power provided by the magneticfield between the pole pieces 31 and 32 commonly provide the focusingpower of the objective lens 19 of the particle beam system 1.

A controller 39 is provided for supplying suitable voltages to theterminal electrode 36, the end electrode 37, the cathode 7 and theextractor and suppressor electrodes 9 such that an electron beam focusis formed in the object plane.

These voltages can be selected such that the electrons of the primaryelectron beam have a predetermined kinetic energy when they are incidenton the object 25 at location 21. It is in particular possible that thecontroller 39 supplies a voltage corresponding to ground potential or avoltage differing from ground potential to the terminal electrode 36.

The objective lens 19 further includes deflectors 41 which are alsocontrolled by the controller 39 for deflecting the electron beam 13 andfor varying the location 21 at which the primary electron beam 13 isincident, on the object 25 in the object plane 23. By deflecting theprimary electron beam it is in particular possible to systematicallyscan the primary particle beam across a portion of the surface of theobject 25.

The primary particle beam incident, on the object 25 results in thatsecondary electrons emerge from the object 25. A portion of suchsecondary electrons may enter into the beam tube 35 such that they aredetected by lee electron detector 17. In the context of the presentapplication, the term secondary electrons comprises all types ofelectrons which are caused to emerge from the object by directing theprimary particle beam onto the object and which can be detected by theelectron detector 17. The term secondary electrons in particularincludes backscattered electrons having a kinetic energy whichcorresponds to or is somewhat smaller than the kinetic energy of theprimary particles incident on the object. The term further includessecondary electrons having, when they emerge from the surface of theobject, a kinetic energy which is substantially smaller than the kineticenergy of the primary particles upon their incidence onto the object.FIG. 1 schematically shows an exemplary trajectory of a secondaryelectron which is incident on the electron detector 17 at referencenumeral 43.

The particle beam system 1 further comprises an X-ray detector 47disposed in between of the objective lens 19 and the object plane 23.The X-ray detector 47 comprises a central aperture 49 allowing theprimary particle beam 13 and secondary electrons 43 to traverse theX-ray detector 47. The X-ray detector 47 comprises plural detectionsurfaces 51 for X-ray detection, wherein the plural detection surfaces51 are located at a radial distance from a main axis 12 of the objectivelens. The X-ray detector 47 is provided for detecting X-rays generatedby the primary particle beam 13 incident on the object. An exemplarytrajectory of an X-ray generated by the primary electron beam 13 atlocation 21 and incident, on the X-ray detector 47 is indicated in FIG.1 at reference numeral 53.

A configuration of the X-ray detector 47 is illustrated as a sectionalview in FIG. 2 and as an elevational view in FIG. 3. The X-ray detector47 comprises a ring-shaped carrier including an upper plate 55 having acentral bore for providing the aperture 49 allowing the primary particlebeam 13 and the secondary electrons 43 to pass through. Foursemiconductor detectors are attached to a bottom surface of plate 55such that a detection surface 59 of each semiconductor detector 57 isoriented towards the object plane 23. A membrane or window 61 is mountedin front of the detection surface 59 of each semiconductor detector 57.The membranes 61 have a function to at least partially prevent incidenceof secondary electrons on the detection surfaces 59 of the semiconductordetectors 57. In the exemplary embodiment shown in FIG. 2, the membrane61 is disposed at a small distance from the detection surface 59. It is,however, also possible that the membrane contacts or is directlyattached as a membrane layer to the detection surface of thesemiconductor detector and such that the membrane is carried by thesemiconductor detector.

The membranes 61 can be configured such that they are not fixedlyattached to the semiconductor detector or the ring structure such thatthey can be readily removed and replaced by other membranes. Theexemplary embodiment shown in FIGS. 2 and 3 has axial projections 63provided on the plate 55. The projections 63 include radially extendingportions 65 adapted to carry the membranes 61 such that they are mountedon the X-ray detector 47. For example, the membranes 61 can be clampedbetween the radial projections 65 and an outer axial ring-shapedprojection 66 provided on the plate 55.

In the embodiment shown in FIGS. 2 and 3, the X-ray detector 57comprises four separate semiconductor detectors arranged in aconfiguration of four quadrants distributed around the aperture 49. Thefour semiconductor detectors 57 each have a same configuration and sameproperties, and detection signals of the four semiconductor detectors 57are separately received by the controller 39.

The four membranes 61 arranged in front of the detection surfaces 59 ofthe four semiconductor detectors have different properties. Twodifferent types of membranes are provided. Two membranes which areindicated by reference numeral 61 in FIG. 3 have a transmittance forsecondary electrons which is greater than a transmittance for secondaryelectrons of the two other membranes which are indicated in FIG. 3 withreference numeral 61′.

The two different types of membranes having different transmittances forsecondary electrons are provided to reduce a detection efficiency forsecondary electrons of the X-ray detector, while a detection efficiencyfor X-rays is not substantially reduced. The membranes having thediffering transmittances for secondary electrons can be in particularused for determining an amount of detected secondary electrons and todetermine a remaining amount of detected X-rays. This may improve anaccuracy of X-ray detection.

The membranes 61 are made from a material including elements having alow atomic number such that a transmittance for X-rays is high. Allmembranes can be made from the same material and have differentthicknesses for providing the different transmittances for secondaryelectrons. The membranes can be made of polyester, for example. Examplesof suitable polyesters include terephtalat-polyester, such aspolyethylenterephtalat-polyester. Suitable membranes can be obtainedfrom the company DuPont, Wilmington, USA under the product name Mylar.Suitable thicknesses of the membranes can be for example, within a rangefrom 0.1 μm to 50 μm, and in particular from 1.0 μm to 10 μm. Othersuitable membranes can be obtained from the company MoxTek, Orem, USAunder the product name AP3.3. Still further membranes can be made ofberyllium, for example.

In an exemplary embodiment illustrated with reference to FIGS. 4 and 5below, a membrane having the greater transmittance for electrons isprovided by a foil having a thickness of 1 μm made of the materialAP3.3, and a membrane having a lower transmittance for electrons is madeof a foil of a thickness of 6 μm of the material Mylar.

FIG. 4 shows a graph representing transmittances for electrons independence on kinetic energy of the electrons for the two membranesobtained by numerical simulation.

FIG. 5 shows a graph representing transmittances for X-rays independence on kinetic energy of the electrons for the two membranesobtained by numerical simulation.

In the example illustrated with reference to FIG. 6 below, a membranehaving the greater transmittance for electrons is provided by a foil ofa thickness of 1 μm of Mylar material, and a membrane having the smallertransmittance for electrons is provided by a foil having a thickness of6 μm of the same Mylar material.

FIG. 6 shows graphs representing count rates measured in an experimentusing the semiconductor detectors 47 of the particle beam system 1 shownin FIG. 1. In this experiment, the primary particle beam is directedonto a sample made of manganese (Mn). The graphs shown in FIG. 6illustrate a number of detection events recorded in a given time by thesemiconductor detector having the thin foil located in front of it and anumber of detection events recorded at the given time by thesemiconductor detector having the thick foil located in front of it.Each graph is plotted in dependence on a kinetic energy of primaryparticles incident on the sample. From FIG. 6 it appears that the countrates for the thin membrane and for the thick membrane differ withrespect to their dependency on energy such that it is possible by afurther analysis to derive additional information from the detectionsignals. It is in particular possible to determine an amount ofdetection signals caused by detected X-rays.

In the example illustrated above, the X-ray detector comprises fourseparate semiconductor detectors. It is, however, also possible to use anumber of semiconductor detectors which differs from four. Two, three,five, six or more semiconductor detectors can be used, for example. Twodifferent types of membranes having different transmittances forsecondary electrons are used in the exemplary embodiment illustratedabove. It is, however, also possible to use a higher number of membraneshaving different transmittances for secondary electrons. For example,three or more membranes having different transmittances for secondaryelectrons can be used.

Detection signals generated by the semiconductor detectors 57 anddetection signals generated by the electron detectors 17 are supplied tothe controller 39. Electron microscopic images can be generated from thedetection signals of the semiconductor detectors and from the detectionsignal of the electron detector. This can be achieved by controlling thedeflectors 41 such that the primary particle beam 13 is scanned todifferent locations 21 on the sample 25 and by recording detectedintensities in correspondence with the respective locations. Theobtained images can be displayed on a monitor 81, and a controller 39,which may comprise a computer, can be controlled by a suitable inputdevice, such as a keyboard 82. The controller may include a module toanalyze the varying detection signals. In particular, the detectionsignals obtained from the semiconductor detector having the membrane 61located in front of it and the detection signals from the semiconductordetector having the membrane 61′ located in front of it, and thedetection signals obtained from the electron detector 17 can be comparedand analyzed relative to each other for obtaining derived measurementvalues from the detection signals. Such derived measurement values canalso be displayed in dependence on the respective locations 21 asimages.

FIG. 7 shows a further example of a particle beam system. The particlebeam system 1 a shown in FIG. 7 has a similar configuration as theparticle beam system illustrated above with reference to FIGS. 1 and 6.The particle beam system 1 a again comprises an objective lens 19 ahaving an X-ray detector 47 a located in front of it. The X-ray detector47 a comprises a semiconductor detector 57 having a detection surface,wherein a membrane 61 a is located in front of the detection surface andbetween the detection surface and an object plane of the objective lens19 a. A membrane 73 is mounted on a ring-shaped carrier 71 providedbetween the X-ray detector 47 a and the object plane 23 a. The carrier71 is mounted on a rod 75 extending through a wall 77 defining a vacuumspace in which the objective lens 19 a is arranged. A motor 81 isprovided as an actuator which is controlled by a controller not shown inFIG. 7 and corresponding to controller 39 shown in FIG. 1. The rod 75can be displaced back and forth in a longitudinal direction of the rod75 by operating the actuator 81, as indicated by a double arrow 83 inFIG. 7. It is thus possible to arrange the membrane 73 in a firstposition in front of the detector 47 a, and to arrange the membrane in asecond position in which it is not disposed between the detector 47 aand the object plane 23. In the first and second positions, the membrane73 provides different transmittances for electrons such that it ispossible to change a detection characteristic of the semiconductordetector for X-ray radiation by controlling the actuator 81.

The membrane 61 a, which is carried by the X-ray detector 47 a in theexemplary embodiment illustrated in FIG. 7 can be omitted, while thedetection efficiency of the semiconductor detector for electrons canstill be changed by displacing the membrane 73 under the control of theactuator 81.

FIG. 8 is a partial view of a further exemplary embodiment of a particlebeam system, wherein the particle beam system 1 b shown in FIG. 8 issimilar to the particle system illustrated with reference to FIG. 7above. FIG. 8 is an elevational view from the bottom of an X-raydetector 47 b as it can be seen from an object plane (see referencenumeral 23 a in FIG. 7) of an objective lens of the particle beam system1 b. Membranes 73 b and 73 b′ mounted on a carrier 71 b can beselectively positioned in front of an X-ray detector 47 b. The carrier71 b is mounted on a rod 75 b which can be displaced by an actuator (notshown in FIG. 8) as indicated by a double arrow 83 b in FIG. 8. Themembranes 73 b and 73 b′ differ with respect to a transmittance forsecondary electrons. In the example shown in FIG. 8, the X-ray detector47 b includes four semiconductor detectors, wherein each of thesemiconductor detectors has a detection surface 59 b. An additionalmembrane can be provided in front of some or more of the detectionsurfaces. If two or more membranes are provided in front of thedetection surfaces, they can also differ with respect to theirtransmittance for secondary electrons. It is also possible to provide anumber of semiconductor detectors which is different than four. It is inparticular possible, to provide only one single semiconductor detectorwhile still providing the possibility of obtaining measurements atdifferent transmittances for secondary electrons since differentmembranes 73 b and 73 b′ are mounted on the carrier 71 b. The membranes73 b and 73 b′ differ with respect to their secondary electrontransmittances and can be selectively positioned in front of the X-raydetector.

In the embodiment shown in FIG. 8, it is also possible that only themembrane 73 b is mounted on the carrier 71 b while the membrane 73 b′ isomitted. With such configuration it is still possible to obtain twomeasurements differing with respect to the secondary electrontransmittance, if the carrier 71 b is reciprocated between its twopositions.

The one or more membranes mounted on the carrier in the embodimentsillustrated with reference to FIGS. 7 and 8 above can be made ofmaterials and thicknesses as illustrated with respect to the membranes61 in the embodiments illustrated with reference to FIGS. 1 to 6 above.

It is further possible to arrange the motor providing the actuatorwithin the wall 77 and inside the vacuum space.

It is further possible that the actuator is a manually operated actuatorrather than an actuator operated by a motor.

In the embodiments illustrated above, the particle beam system is anelectron beam system in which an electron beam is used as the primaryparticle beam for releasing electrons and X-rays from a sample. It is,however, also possible that an ion beam rather than the electron beam isused as the primary electron beam to release electrons and X-rays fromthe sample. Examples of suitable systems for generating an ion beam asthe primary particle be are known from US 2007/0228287 A1 and US2007/0215802 A1, wherein the full disclosure of these documents isincorporated herein by reference.

According to embodiments, there is provided a particle beam systemcomprising a particle beam source for generating a primary particlebeam, an objective lens for focusing the primary particle beam, anelectron detector and an X-ray detector. The X-ray detector comprisesone or more semiconductor detectors having detection surfaces orientedtowards a sample. One or more membranes can be selectively providedbetween the one or more detection surfaces and the sample. If two ormore membranes are provided, they may differ with respect to atransmittance for secondary electrons.

While the invention has been described with respect to certain exemplaryembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, the exemplary embodiments of the invention set forth hereinare intended to be illustrative and not limiting in any way. Variouschanges may be made without departing from the spirit and scope of thepresent invention as defined in the following claims.

1-20. (canceled)
 21. A particle beam system comprising: a particle beamsource configured to generate a primary particle beam; an objective lensconfigured to focus the primary particle beam in an object plane; anX-ray detector arranged between the objective lens and the object plane;and a controller; wherein the X-ray detector comprises: a semiconductordetector having a detection surface oriented towards the object plane,the detection surface being sensitive to both X-rays and secondaryelectrons; and a membrane disposed between the object plane and thedetection surface, wherein the membrane partly prevents an incidence ofsecondary electrons on the detection surface; and wherein the controllerincludes a module configured to analyse detection signals of thesemiconductor detector to determine an amount of detection events causedby X-rays and to determine an amount of detection events caused bysecondary electrons.
 22. The particle beam system of claim 21, whereinthe membrane does not substantially reduce the detection efficiency ofthe semiconductor detector for X-rays.
 23. The particle beam system ofclaim 21, wherein the membrane has a thickness selected such thatcharacteristic X-ray peaks of a sample positioned in the object planecan be identified in the detection signals of the semiconductordetector.
 24. The particle beam system of claim 21, wherein thesemiconductor detector is mounted on a ring structure surrounding a beampath of the primary particle beam.
 25. The particle beam system of claim21, further comprising a deflector configured to direct the primaryparticle beam to different locations on the object plane.
 26. Theparticle beam system of claim 25, wherein the module of the controlleris configured to control the deflector such that the primary particlebeam is scanned across a portion of the object plane and such that animage is generated based on the detection signals generated by thesemiconductor detector.
 27. A detector system comprising: asemiconductor detector having a detection surface, the detection surfacebeing sensitive to both X-rays and secondary electrons; a membranedisposed in front of the detection surface, wherein the membrane partlyprevents an incidence of secondary electrons on the detection surface;and a controller; wherein the detector is configured for simultaneousdetection of X-rays and secondary electrons released from a sample dueto interaction of a primary particle beam with the sample; and whereinthe controller includes a module configured to analyse detection signalsof the semiconductor detector to determine an amount of detection eventscaused by X-rays and to determine an amount of detection events causedby secondary electrons.
 28. The detector of claim 27, wherein themembrane does not substantially reduce the detection efficiency of thesemiconductor detector for X-rays.
 29. The detector of claim 28, whereinthe membrane has a thickness selected such that characteristic X-raypeaks of a sample positioned in the object plane can be identified inthe detection signals of the semiconductor detector.
 30. The detector ofclaim 27, wherein the semiconductor detector is mounted on a ringstructure having a central aperture for passing through a beam path ofthe primary particle beam.